The present invention relates to a brush holder provided in an AC generator for use in vehicles, in which a brush is inserted into a brush box and depressed by a compression spring.
FIG. 6 shows a cross sectional view of an AC generator for vehicles, which includes a brush holder mounted thereon. In FIG. 6, a stator 1 has a stator iron core 2 and a stator coil 3. On the other hand, a rotor 4 has pole iron cores 5 and 6, having different polarities, which are arranged so that respective pole teeth portions thereof extend alternately in the axial direction of thereof, an exciting coil 7 fixed between the two pole iron cores 5 and 6, a rotary shaft 8 onto which the two iron cores 5 and 6 are fixed, a pair of slip rings 9 fixed to the rotary shaft 8, and fans 10 and 11 fixed to the pole iron cores 5 and 6, respectively.
The stator iron core 2 is fixed to front and rear brackets 12 and 13 by means of a clamp bolt 14. The rotary shaft 8 is supported by bearings 15 and 16 provided in the front and rear brackets 12 and 13, respectively. A pulley 17 is fixed to the rotary shaft 8 so as to transmit the rotation of an engine to the rotary shaft 8 to thereby rotate the rotor 4.
A rectifier device 18 rectifies, into a direct current, an alternating current generated from an alternating voltage induced by the stator coil 3. A voltage regulator 19 detects a generator voltage and controls an exciting current to regulate a terminal voltage to a predetermined value.
A brush holder 20 is fixed to the rear bracket 13. A brush 28 is held and depressed by the brush holder 20 so as to allow its upward and downward movement. A partition ring 22 is fixed to the rear bracket 13 so as to sealingly surround the slip rings 9 to prevent harmful substances such as moisture and salinity in the ambient air from damaging the slip rings 9.
FIGS. 5A and 5B respectively show a plane view and a partially sectioned frontal view, each showing a conventional brush holder to be mounted onto the above-noted AC generator. The brush holder 20 includes a brush box 21 made of synthetic resin, into which the brush 28 is inserted, a connector portion 23, a terminal portion 24, a compression spring 25 for depressing the brush 28, an electrode portion 26 which is a tip end portion of a connection conductor embedded in the brush box 21, and a cover 27 made of synthetic resin.
A connection lead 29 extending from the brush 28 is pulled out from the brush box 21 through a hole formed in an upper wall of the brush box 21 so that the tip end of the connection lead 29 is wound onto the electrode portion 26 and soldered thereto.
The conventional brush holder for an AC generator used in vehicles, however, suffers from a problem in that mounting of the brush 28 onto the brush holder 20 is difficult since the mounting must be performed by inserting the brush 28 into the brush box 21 in a direction indicated by an arrow A in FIG. 5B, pulling out the tip end of the lead 29 upwardly from the brush box 21, winding the tip end onto the electrode portion 26, and soldering the tip end onto the electrode portion 26. Further, since the tip end of the lead 29 is wound and soldered onto the electrode portion 26, if the soldered portion of the lead 29 is excessive in length, the other free portion of the lead 29 becomes shortened. As a result, the brush 28 is pulled by the lead 29 and the movement of the brush 28 is restricted, due to the shortened length of the lead 29, before the brush 28 reaches its abrasion limit of the brush 28.
Furthermore, when the brush is changed because of wear, it is necessary that the tip end of the lead 29 of the brush 28 be unsoldered, the brush removed from the brush box 21 downwardly, the other new brush 28 inserted into the brush box 21 upwardly, a tip end of a lead 29 of the other new brush 28 pulled out from the brush box 21, and wound and soldered onto the electrode portion 27. Accordingly, changing a brush 28 requires much time and special skill.